docs: def create_lockfile(self):
          """
          Write recursive dependencies list to outfile
          with hard-pinned versions.
          Then fix it.
          """
          process = subprocess.Popen(
              self.pin_command,
              stdout=subprocess.PIPE,
              stderr=subprocess.PIPE,
          )
          stdout, stderr = process.communicate()
          if process.returncode == 0:
              self.fix_lockfile()
          else:
              logger.critical("ERROR executing %s", ' '.join(self.pin_command))
              logger.critical("Exit code: %s", process.returncode)
              logger.critical(stdout.decode('utf-8'))
              logger.critical(stderr.decode('utf-8'))
              raise RuntimeError("Failed to pip-compile {0}".format(self.infile))